Electronic circuits including diode-connected bipolar junction transistors

ABSTRACT

A diode-connected bipolar junction transistor includes a common collector region of a first conductivity, a common base region of a second conductivity disposed over the common collector region, and a plurality of emitter regions of the first conductivity disposed over the common base region, arranged to be spaced apart from each other, and arranged to have island shapes. The common base region and the common collector region are electrically coupled to each other.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.14/322,775, filed on Jul. 2, 2014, which claims priority of Koreanpatent application number 10-2014-0014897, filed on Feb. 10, 2014. Thedisclosure of each of the foregoing applications is incorporated hereinby reference in its entirety.

BACKGROUND

1. Technical Field

Various embodiments of the present disclosure relate to electroniccircuits including bipolar junction transistors.

2. Related Art

A power supply voltage applied to an integrated circuit may vary due tovarious factors. The variation of the power supply voltage may affectoperation currents of the integrated circuit and may even causemalfunctions of the integrated circuits. Thus, it is important to designa reference voltage generator or a reference current generator thatproduces a constant voltage level or a constant amount of currentregardless of the variation of the power supply voltage. It is alsoimportant to minimize temperature sensitivity of the reference voltagegenerator or the reference current generator.

A reference voltage may be obtained by generating a constant voltagebased on a band gap voltage of a silicon material. In general, areference voltage circuit may include a pair of bipolar junctiontransistors, which have different current densities, and are coupled inparallel. In such a case, while an emitter-base voltage of each of thebipolar junction transistors has a positive temperature coefficient, avoltage difference between the emitter-base voltages of the pair ofbipolar junction transistors may have a negative temperaturecoefficient. If the positive temperature coefficient and the negativetemperature coefficient may be appropriately controlled to have the sameabsolute value, the reference voltage circuit may generate a constantreference voltage regardless of temperature variation. This referencevoltage is known as close to the band gap voltage of the siliconmaterial at zero (0) degree of the absolute temperature (OK). Also, thisreference voltage circuit is referred to as a band gap reference (BGR)circuit. The BGR circuit is known as stable to the temperaturevariation, and widely used in integrated circuits. That is, if collectorresistance values of the bipolar junction transistors may beappropriately controlled to cancel the positive temperature coefficientand the negative temperature coefficient of the bipolar junctiontransistors, the BGR circuit may generate a stable and constantreference voltage regardless of temperature variation. However, if thebipolar junction transistors are employed in the BGR circuit, theintegration density of the BGR circuit may be degraded.

SUMMARY

Various embodiments are directed to electronic circuits includingbipolar junction transistors.

According to an embodiment, an electronic circuit may include adiode-connected bipolar junction transistor. The diode-connected bipolarjunction transistor may include a common collector region of a firstconductivity, a common base region of a second conductivity disposedover the common collector region, and a plurality of emitter regions ofthe first conductivity disposed over the common base region, arranged tobe spaced apart from each other, and arranged to have island shapes. Thecommon base region and the common collector region are electricallycoupled to each other

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments will become more apparent in view of the attacheddrawings and accompanying detailed description, in which:

FIG. 1 is a layout diagram illustrating a diode-connected bipolarjunction transistor according to an embodiment;

FIG. 2 is a cross-sectional view taken along line I-I′ of FIG. 1;

FIG. 3 is an equivalent circuit diagram of a diode-connected bipolarjunction transistor shown in FIG. 1;

FIG. 4 is a layout diagram illustrating a diode-connected bipolarjunction transistor according to an embodiment;

FIG. 5 is a layout diagram illustrating a diode-connected bipolarjunction transistor according to an embodiment;

FIG. 6 is a cross-sectional view taken along line II-II′ of FIG. 5;

FIG. 7 is an equivalent circuit diagram of a diode-connected bipolarjunction transistor shown in FIG. 5;

FIG. 8 is a layout diagram illustrating a diode-connected bipolarjunction transistor according to an embodiment;

FIG. 9 is a circuit diagram illustrating an electronic circuit includinga diode-connected bipolar junction transistor according to anembodiment; and

FIG. 10 is a circuit diagram illustrating an electronic circuitincluding a diode-connected bipolar junction transistor according to anembodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following embodiments may provide diode-connected bipolar junctiontransistors, and each of the diode-connected bipolar junctiontransistors may include a plurality of vertical bipolar junctiontransistors that share a single common collector region and a singlecommon base region with a plurality of separate emitter regions. Thesediode-connected bipolar junction transistors may be used to realizecircuits for generating reference voltages in memory devices ornon-memory devices. The memory devices may include dynamic random accessmemory (DRAM) devices, static random access memory (SRAM) devices, flashmemory devices, magnetic random access memory (MRAM) devices, phasechangeable random access memory (PcRAM) devices, resistive random accessmemory (ReRAM) devices or ferroelectric random access memory (FeRAM)devices. The non-memory devices may include logic devices employingoperational amplifiers (OP-AMPs), multi-stage amplifiers, senseamplifiers or the like.

In the following embodiments, it will be understood that when an elementis referred to as being located “on”, “over”, “above”, “under”,“beneath” or “below” another element, it may directly contact the otherelement, or at least one intervening element may also be presenttherebetween. Accordingly, the terms such as “on”, “over”, “above”,“under”, “beneath”, “below” and the like that are used herein are forthe purpose of describing particular embodiments only and are notintended to limit other embodiments.

Referring to FIGS. 1 and 2, a diode-connected bipolar junctiontransistor 100 according to an embodiment may include a plurality ofN-P-N type bipolar junction transistors coupled in parallel. Each of theplurality of bipolar junction transistors may have a diode-connectedstructure in which a base region and a collector region of the bipolarjunction transistor are electrically coupled to each other.Specifically, an N-type common collector region 120 may be disposed overa substrate 110. A P-type common base region 130 and N-type collectorcontact regions 122 and 124 may be disposed over the N-type commoncollector region 120. The N-type collector contact regions 122 and 124may have greater impurity concentration than the impurity concentrationof the N-type common collector region 120. The P-type common base region130 may be surrounded by the N-type common collector region 120. Aplurality of N-type emitter regions, for example, nine (9) N-typeemitter regions 141 to 149 and P-type base contact regions 132 and 134may be disposed over the P-type common base region 130. The N-typeemitter regions 141 to 149 may be arrayed in one direction parallel witha top surface of the substrate 110, and may be spaced apart from eachother to have island shapes. The P-type base contact regions 132 and 134may have greater impurity concentration than the impurity concentrationof the P-type common base region 130.

The N-type collector contact regions 122 and 124, the P-type basecontact regions 132 and 134, and the N-type emitter regions 141 to 149may be separated from each other by an isolation layer 150 disposed inthe substrate 130. That is, the isolation layer 150 may be disposedbetween the N-type collector contact regions 122 and 124, the P-typebase contact regions 132 and 134, and the N-type emitter regions 141 to149. For example, the isolation layer 150 may be a trench isolationlayer. The isolation layer 150 may have a thickness of about 300nanometers. The N-type collector contact regions 122 and 124, the P-typebase contact regions 132 and 134, and the N-type emitter regions 141 to149 may have a depth of about 20% to about 40% of the thickness of theisolation layer 150. For example, when the isolation layer 150 has athickness of about 300 nanometers, the N-type collector contact regions122 and 124, the P-type base contact regions 132 and 134, and the N-typeemitter regions 141 to 149 may have a depth of about 60 nanometers toabout 120 nanometers. For example, contact areas between each of theN-type emitter regions 141 to 149 and the P-type common base region 130may be substantially the same. The current drivability of each of thevertical bipolar junction transistors including the N-type emitterregions 141 to 149 may depend on the area of the contact surface Lbetween each of the N-type emitter regions 141 to 149 and the P-typecommon base region 130. Thus, the current drivability of each of thevertical bipolar junction transistors including the N-type emitterregions 141 to 149 may be substantially the same.

One of the N-type emitter regions 141 to 149, for example, the N-typeemitter region 141 may be electrically coupled to a first emitter nodeE1, and the other N-type emitter regions 141 to 149 may be electricallycoupled to a second emitter node E2. For example, the emitter region 141coupled to the first emitter node E1 may be disposed at the center ofthe N-type emitter regions 141 to 149 to improve the matchingcharacteristics of the vertical bipolar junction transistors includingthe N-type emitter regions 141 to 149. The N-type collector contactregions 122 and 124 and the P-type base contact regions 132 and 134 maybe electrically coupled to a collector node C to realize adiode-connected structure.

Referring to FIG. 3, all of the collectors of the nine (9) bipolarjunction transistors 191 to 199 may be electrically coupled to thecollector node C. Each of the bipolar junction transistors 191 to 199may have a collector and a base coupled to each other. Thus, each of thebipolar junction transistors 191 to 199 may function as a diode-typebipolar junction transistor. That is, all of the bases and thecollectors of the bipolar junction transistors 191 to 199 may be coupledto the collector node C. An emitter of the bipolar junction transistor191 may be electrically coupled to the first emitter node E1, andemitters of the remaining bipolar junction transistors 192 to 199 may beelectrically coupled to the second emitter node E2. As described withreference to FIGS. 1 and 2, all of the bipolar junction transistors 191to 199 may share a single base, i.e., the P-type common base region 120,and a single collector, i.e., the N-type common collector region 130.The bipolar junction transistors 191 to 199 may include nine (9)separate emitters, i.e., the emitter regions 141 to 149, respectively.

Referring to FIG. 4, a diode-connected bipolar junction transistor 200according to an embodiment may include a plurality of N-P-N type bipolarjunction transistors connected in parallel, and each of the N-P-N typebipolar junction transistors may function as a diode-type bipolarjunction transistor whose base region and collector region areelectrically coupled to each other. That is, a P-type common base region230 may be disposed in an N-type common collector region 220, and aplurality of N-type emitter regions, for example, nine (9) N-typeemitter regions 241 to 249, may be disposed in the P-type common baseregion 230 to be spaced apart from each other. The N-type emitterregions 241 to 249 may be disposed in array. For example, the N-typeemitter regions 241 to 249 may be arrayed in three rows parallel with afirst direction, and in three columns parallel with a second direction.The diode-connected bipolar junction transistor 200 according to thepresent embodiment may be the same as the diode-connected bipolarjunction transistor 100 described with reference to FIGS. 2 and 3 exceptthat the N-type emitter regions 241 to 249 are disposed in array.

Referring to FIGS. 5 and 6, a diode-connected bipolar junctiontransistor 300 according to an embodiment may include a plurality ofP-N-P type bipolar junction transistors coupled in parallel. Each of theplurality of bipolar junction transistors may have a diode-connectedstructure in which a base region and a collector region of the bipolarjunction transistor are electrically coupled to each other.Specifically, a P-type common collector region 320 may be disposed overa substrate 310. When the substrate 310 is a P-type substrate, thesubstrate 310 may serve as the P-type common collector region 320. AnN-type common base region 330 and P-type collector contact regions 322and 324 may be disposed over the P-type common collector region 320. TheP-type collector contact regions 322 and 324 may have greater impurityconcentration than the impurity concentration of the P-type commoncollector region 320. The N-type common base region 330 may besurrounded by the P-type common collector region 320. A plurality ofP-type emitter regions, for example, nine (9) P-type emitter regions 341to 349 and N-type base contact regions 332 and 334 may be disposed overthe N-type common base region 330. The P-type emitter regions 341 to 349may be arrayed in one direction parallel with a top surface of thesubstrate 310, and may be spaced apart from each other to have islandshapes. The N-type base contact regions 332 and 334 may have greaterimpurity concentration than the impurity concentration of the N-typecommon base region 330.

The P-type collector contact regions 322 and 324, the N-type basecontact regions 332 and 334, and the P-type emitter regions 341 to 349may be separated from each other by an isolation layer 350 disposed inthe substrate 330. That is, the isolation layer 350 may be disposedbetween the P-type collector contact regions 322 and 324, the N-typebase contact regions 332 and 334, and the P-type emitter regions 341 to349. For example, the isolation layer 350 may be a trench isolationlayer. The isolation layer 350 may have a thickness of about 300nanometers. The P-type collector contact regions 322 and 324, the N-typebase contact regions 332 and 334, and the P-type emitter regions 341 to349 may have a depth of about 20% to about 40% of the thickness of theisolation layer 350. For example, when the isolation layer 350 has athickness of about 300 nanometers, the P-type collector contact regions322 and 324, the N-type base contact regions 332 and 334, and the P-typeemitter regions 341 to 349 may have a depth of about 60 nanometers toabout 120 nanometers. For example, contact areas between each of theP-type emitter regions 341 to 349 and the N-type common base region 330may be substantially the same. The current drivability of each of thevertical bipolar junction transistors including the P-type emitterregions 341 to 349 may depend on the area of the contact surface Lbetween each of the P-type emitter regions 341 to 349 and the N-typecommon base region 330. Thus, the current drivability of each of thevertical bipolar junction transistors including the P-type emitterregions 341 to 349 may be substantially the same.

One of the P-type emitter regions 341 to 349, for example, the P-typeemitter region 341, may be electrically coupled to a first emitter nodeE1, and the other P-type emitter regions 341 to 349 may be electricallycoupled to a second emitter node E2. For example, the emitter region 341coupled to the first emitter node E1 may be disposed at the center ofthe P-type emitter regions 341 to 349 to improve matchingcharacteristics of the vertical bipolar junction transistors includingthe P-type emitter regions 341 to 349. The P-type collector contactregions 322 and 324 and the N-type base contact regions 332 and 334 maybe electrically coupled to a collector node C to realize adiode-connected structure.

Referring to FIG. 7, all of the collectors of the nine (9) bipolarjunction transistors 391 to 399 may be electrically coupled to thecollector node C. Each of the bipolar junction transistors 391 to 399may have a collector and a base coupled to each other. Thus, each of thebipolar junction transistors 391 to 399 may function as a diode-typebipolar junction transistor. That is, all of the bases and thecollectors of the bipolar junction transistors 391 to 399 may be coupledto the collector node C. An emitter of the bipolar junction transistor391 may be electrically coupled to the first emitter node E1, andemitters of the remaining bipolar junction transistors 392 to 399 may beelectrically coupled to the second emitter node E2. As described withreference to FIGS. 5 and 6, all of the bipolar junction transistors 391to 399 may share a single base, i.e., the N-type common base region 320,and a single collector, i.e., the P-type common collector region 330.The bipolar junction transistors 391 to 399 may include nine (9)separate emitters, i.e., the emitter regions 341 to 349, respectively.

Referring to FIG. 8, a diode-connected bipolar junction transistor 400according to an embodiment may include a plurality of P-N-P type bipolarjunction transistors coupled in parallel, and each of the P-N-P typebipolar junction transistors may function as a diode-type bipolarjunction transistor whose base region and collector region areelectrically coupled to each other. That is, an N-type common baseregion 430 may be disposed in a P-type common collector region 420, anda plurality of P-type emitter regions, for example, nine (9) P-typeemitter regions 441 to 449, may be disposed in the N-type common baseregion 430 to be spaced apart from each other. The P-type emitterregions 441 to 449 may be disposed in array. For example, the P-typeemitter regions 441 to 449 may be arrayed in three rows parallel with afirst direction, and in three columns parallel with a second direction.The diode-connected bipolar junction transistor 400 according to thepresent embodiment may be the same as the diode-connected bipolarjunction transistor 300 described with reference to FIGS. 5 and 6 exceptthat the P-type emitter regions 441 to 449 are disposed in array.

Referring to FIG. 9, an electronic circuit 500 may be a band gapreference (BGR) circuit. The electronic circuit 500 may include threeresistors 521, 522 and 523, an operational amplifier 510, and adiode-connected bipolar junction transistor 100. The diode-connectedbipolar junction transistor 100 may be the one described with referenceto FIGS. 1, 2 and 3. When a power supply voltage VDD is applied to thecollectors of the N-P-N type bipolar junction transistors 191 to 199, acollector current may flow through the N-P-N type bipolar junctiontransistors 191 to 199. As a result, a first emitter-base voltage VBE1may be generated between the first emitter node E1 and the base, i.e.,the power supply voltage VDD, of the N-P-N type bipolar junctiontransistor 191, and a second emitter-base voltage VBE2 may be generatedbetween the second emitter node E2 and the bases, i.e., the power supplyvoltage VDD, of the N-P-N type bipolar junction transistors 192 to 199.

The first emitter node E1 of the bipolar junction transistor 191 may becoupled to a first node of the resistor 521 at a node A, and the secondemitter node E2 of the bipolar junction transistors 192 to 199 may becoupled to a first node of the resistor 523. The first node of theresistor 521 and a positive input node of the operational amplifier 510may be coupled to each other at the node A. A second node of theresistor 523, a first node of the resistor 522 and a negative input nodeof the operational amplifier 510 may be electrically coupled in commonat a node B. Second nodes of the resistors 521 and 522 may beelectrically coupled to an output node Vout of the operational amplifier510.

The operational amplifier 510 may normalize voltages of the nodes A andB to output a band gap voltage through the output node Vout thereof. Theband gap voltage, that is, a band gap reference voltage V_(REF) may berepresented by the following equation 1.

$\begin{matrix}{V_{REF} = {{VDD} - \left\lfloor {V_{{BE}\; 2} + {\left( {1 + \frac{R_{2}}{R_{3}}} \right) \cdot {\ln(n)} \cdot V_{T}}} \right\rfloor}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

In Equation 1, “VDD” denotes the power supply voltage, “V_(BE2)” denotesthe voltage between the second emitter node E2 and the bases of thebipolar junction transistors 192 to 199, “R2” denotes the resistancevalue of the resistor 522, “R3” denotes the resistance value of theresistor 523, “VT” denotes “kT/q” representing a positive temperaturecoefficient, and “n” denotes the number of bipolar junction transistors192 to 199 coupled in parallel to the second emitter node E2.

As can be seen from equation 1, the band gap reference voltage V_(REF)may be obtained by adding a voltage component V_(BE2) having a negativetemperature coefficient to a voltage component VT having a positivetemperature coefficient. In such a case, when the resistance values R2and R3 are appropriately adjusted such that the negative temperaturecoefficient and the positive temperature coefficient have the sameabsolute value, the band gap reference voltage V_(REF) may have aconstant value regardless of temperature variation.

Referring to FIG. 10, the electronic circuit 600 may be a band gapreference (BGR) circuit. The electronic circuit 600 may include threeresistors 621, 622 and 623, an operational amplifier 610, and adiode-connected bipolar junction transistor 300. The diode-connectedbipolar junction transistor 300 may be the one described with referenceto FIGS. 5, 6 and 7. All of collectors and bases of the bipolar junctiontransistors 391 to 399 may be electrically coupled to a ground voltageVSS. When a bias voltage is applied between the first emitter node E1and the ground voltage VSS, a first collector current may flow throughthe bipolar junction transistor 391 to generate a first emitter-basevoltage (VBE1) between the first emitter node E1 and the base, theground voltage VSS of the P-N-P type bipolar junction transistor 391.Moreover, when a bias voltage is applied between the second emitter nodeE2 and the ground voltage VSS, a second collector current may flowthrough the bipolar junction transistors 392 to 399 to generate a secondemitter-base voltage (VBE2) between the second emitter node E2 and thebase, i.e., the ground voltage VSS of the P-N-P type bipolar junctiontransistors 392 to 399.

The first emitter node E1 of the bipolar junction transistor 391 may becoupled to a first node of the resistor 621 at a node A, and the secondemitter node E2 of the bipolar junction transistors 392 to 399 may becoupled to a first node of the resistor 623. The first node of theresistor 621 and a positive input node of the operational amplifier 610may be coupled to each other at the node A. A second node of theresistor 623, a first node of the resistor 622, and a negative inputnode of the operational amplifier 610 may be electrically coupled incommon at a node B. Second nodes of the resistors 621 and 622 may beelectrically coupled to an output node Vout of the operational amplifier610.

The operational amplifier 610 may normalize voltages of the nodes A andB to output a band gap voltage through the output node Vout thereof. Theband gap voltage, that is, a band gap reference voltage V_(REF) may berepresented by the following equation 2.

$\begin{matrix}{V_{REF} = {V_{{BE}\; 2} + {\left\{ {\left( {1 + \frac{R_{2}}{R_{3}}} \right) \cdot {\ln(n)}} \right\} \cdot V_{T}}}} & {{Equation}\mspace{14mu} 2}\end{matrix}$In Equation 2, “V_(BE2)” denotes the voltage between the second emitternode E2 and the bases of the bipolar junction transistors 392 to 399,“R2” denotes the resistance value of the resistor 622, “R3” denotes theresistance value of the resistor 623, “VT” denotes “kT/q” representingthe positive temperature coefficient, and “n” denotes the number of thebipolar junction transistors 392 to 399 coupled in parallel to thesecond emitter node E2.

As can be seen from Equation 2, the band gap reference voltage V_(REF)may be obtained by adding a voltage component V_(BE2) having a negativetemperature coefficient to a voltage component VT having a positivetemperature coefficient. In such a case, when the resistance values R2and R3 are appropriately adjusted such that the negative temperaturecoefficient and the positive temperature coefficient have the sameabsolute value, the band gap reference voltage V_(REF) may have aconstant value regardless of temperature variation.

The embodiments have been disclosed above for illustrative purposes.Those skilled in the art will appreciate that various modifications,additions and substitutions are possible.

What is claimed is:
 1. An electronic circuit comprising adiode-connected bipolar junction transistor, wherein the diode-connectedbipolar junction transistor comprises: a common collector region of afirst conductivity; a common base region of a second conductivitydisposed over the common collector region; and a plurality of emitterregions of the first conductivity disposed over the common base region,arranged to be spaced apart from each other, and arranged to have islandshapes, wherein the common base region and the common collector regionare electrically coupled to a collector node.
 2. The electronic circuitof claim 1, wherein the diode-connected bipolar junction transistor isan N-P-N type bipolar junction transistor.
 3. The electronic circuit ofclaim 2, wherein a first emitter region of the plurality of emitterregions is coupled to a first emitter node and the others of theplurality of emitter regions are coupled to a second emitter node. 4.The electronic circuit of claim 3, wherein the common base region andthe common collector region are electrically coupled to a power supplyvoltage.
 5. The electronic circuit of claim 4, further comprising anoperational amplifier, wherein a positive input node of the operationalamplifier is electrically coupled to the first emitter node, and anegative input node of the operational amplifier is electrically coupledto the second emitter node.
 6. The electronic circuit of claim 5,further comprising: a first resistor coupled between the first emitternode and an output node of the operational amplifier; a second resistorcoupled between the negative input node and the output node; and a thirdresistor coupled between the negative input node and the second emitternode.
 7. The electronic circuit of claim 1, wherein the diode-connectedbipolar junction transistor is a P-N-P type bipolar junction transistor.8. The electronic circuit of claim 7, wherein a first emitter region ofthe plurality of emitter regions is coupled to a first emitter node andthe others of the plurality of emitter regions are coupled to a secondemitter node.
 9. The electronic circuit of claim 8, wherein the commonbase region and the common collector region are electrically coupled toa ground voltage.
 10. The electronic circuit of claim 9, furthercomprising an operational amplifier, wherein a positive input node ofthe operational amplifier is electrically coupled to the first emitternode and a negative input node of the operational amplifier iselectrically coupled to the second emitter node.
 11. The electroniccircuit of claim 10, further comprising: a first resistor coupledbetween the first emitter node and an output node of the operationalamplifier; a second resistor coupled between the negative input node andthe output node; and a third resistor coupled between the negative inputnode and the second emitter node.